(CNN) -- The minute news broke of the terrorist attacks on Mumbai, India, social media sites like Twitter were inundated with a huge volume of messages.

With more than 6 million members worldwide, an estimated 80 messages, or "tweets," were being sent to Twitter.com via SMS every five seconds, providing eyewitness accounts and updates.

Many Twitter users also sent pleas for blood donors to make their way to specific hospitals in Mumbai where doctors were faced with low stocks and rising casualties.

Others sent information about helplines and contact numbers for those who had friends and relatives caught up in the attacks. Tweeters were also mobilized to help with transcribing a list of the dead and injured from hospitals, which were quickly posted online.

As Twitter user "naomieve" wrote: "Mumbai is not a city under attack as much as it is a social media experiment in action."

Neha Viswanathan, a former regional editor for Southeast Asia and a volunteer at Global Voices, told CNN, "Even before I actually heard of it on the news I saw stuff about this on Twitter.

"People were sending in messages about what they were hearing. There were at least five or six blogs from people who were trapped, or who were very close to what happened."

One tweet from "Dupree" appeared to be coming from inside one of the hotels: "Mumbai terrorists are asking hotel reception for rooms of American citizens and holding them hostage on one floor."

A group of Mumbai-based bloggers turned their Metroblog into a news wire service, while the blog MumbaiHelp offered to help users get through to their family and friends in the city, or to get information about them, and has had a number of successes.

Flickr also proved a useful source of haunting images chronicling the aftermath of the attacks. Journalist Vinukumar Ranganathan's stream of photos were published by CNN and other major broadcasters. iReport.com: Are you there? Share your photos, videos and stories

A Google Map showing the key locations and buildings with links to news stories and eyewitness accounts, and CNN's iReporters flooded the site with their videos and images of the terror attacks.

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However, as is the case with such widespread dissemination of information, a vast number of the posts on Twitter amounted to unsubstantiated rumors and wild inaccuracies.

For example, a rumor that the Indian government was asking tweeters to stop live updates to avoid compromising its security efforts was published and republished on the site.

This was seemingly given credence by at least one major news Web site, which posted the tweet on its live update.

It read simply: "Indian government asks for live Twitter updates from Mumbai to cease immediately. ALL LIVE UPDATES - PLEASE STOP TWEETING."

Then it was suggested via Twitter that terrorists were using the medium to gain information about what Indian security forces were doing, which led to numerous abusive postings urging the terrorists to "die, die, die, if you're reading this."

As blogger Tim Mallon put it, "I started to see and (sic) ugly side to Twitter, far from being a crowd-sourced version of the news it was actually an incoherent, rumour-fueled mob operating in a mad echo chamber of tweets, re-tweets and re-re-tweets.

"During the hour or so I followed on Twitter there were wildly differing estimates of the numbers killed and injured - ranging up to 1,000."

What is clear that although Twitter remains a useful tool for mobilizing efforts and gaining eyewitness accounts during a disaster, the sourcing of most of the news cannot be trusted.

A quick trawl through the enormous numbers of tweets showed that most were sourced from mainstream media.

Someone tweets a news headline, their friends see it and retweet, prompting an endless circle of recycled information.